Automatic analytical devices usually operate on the following principle: samples for analysis or parts of samples are placed in containers and then subjected to a series of processing steps such as adding (pipetting) reagents, mixing or incubation, and measurements of the reactions which have taken place are made a number of times during processing and/or once at the end of processing. The usual procedure is as follows: the containers holding the samples for analysis are placed in a fixed sequence on a conveyor and travel through various processing stations, or in the case of "batch processing", as is usual in the case of "centrifugal analytical devices", all sample containers are placed on a carrier (rotor) and subjected practically simultaneously to the processing steps and measurements. Analytical systems operating on these principles give good service in large clinics and analytical centers where large numbers of samples have to be processed.
In view of the variety of possible analyses today and the medical requirements, particularly in clinical chemistry, it has been found that the automatic analysers conventionally used for throughput of large quantities of samples are insufficiently flexible to provide analytical profiles (full random access) specifically adapted to individual patients or medical conditions, while still being able to handle a large number of samples from patients.